How Resistive Touch Screen Work?

The traditional touch screen technology is analog resistive. These panel work by detecting how much the resistance to current changes when a point is touched. It is accomplished by having two separate layers. Typically, the bottom layer is made of glass and the top layer is a plastic film. When you push down on film it makes contact with glass and completes a circuit.

The glass and plastic film are each covered with grid of electric conductor made up of transparent material, mostly of indium tin oxide (ITO). These conductors runs parallel on each of these sheets. Sheets are arranged such a way that conductors on glass should be right angled to those on the plastic film.

Resistive Touch Technology

When you press down the touch screen, contact is made between grid on the glass and grid on the film. The voltage of the circuit is calculated. X and Y coordinates of the touch position is calculated based on the amount of resistance at the point of contact. This analog signal is converted to Digital form using ADC so as to use by processor as user input.

This technology has lot of disadvantages, however. First, the analog system is susceptible to drift, so the user have to recalibrate the touch panel time to time.

The ITO material used for conductor is brittle. Repetitive use can cause ITO to crack over time and can result in dead spot on the touch screen.

The screen uses this technology usually thicker so as to maintain gap between to sensor planes. The gap between glass and plastic layer of resistive touch panel filled with air. The different refractive index of different layers creates visible artefacts that impact the display quality.

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